Zoom lens and imaging apparatus

ABSTRACT

A zoom lens consists of, in order from the object side, a positive first lens group that is fixed during magnification change, at least two movable lens groups that are moved during magnification change, and a positive end lens group that is disposed at the most image side and is fixed during magnification change. The first lens group consists of, in order from the object side, a negative first-a lens group that is fixed during focusing, a positive first-b lens group that is moved during focusing, and a positive first-c lens group. The first-a lens group includes at least two negative lenses, where the most object-side negative lens has a meniscus shape with the convex surface toward the object side, and a first-n lens, which is at least one negative lens of the rest of the negative lenses of the first-a lens group, satisfies given condition expressions (1) to (3).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to JapanesePatent Application No. 2015-053563, filed on Mar. 17, 2015. The aboveapplication is hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND

The present disclosure relates to a zoom lens for use with electroniccameras, such as digital cameras, video cameras, broadcasting cameras,monitoring cameras, etc., and an imaging apparatus provided with thezoom lens.

For broadcasting cameras and motion picture cameras, change of the angleof view due to focusing is undesirable, and such cameras often employ afocusing system where the first lens group of the zoom lens is dividedinto a first-a lens group that has a negative refractive power and isfixed during focusing, a first-b lens group that has a positiverefractive power, and a first-c lens group that has a positiverefractive power, and the first-b lens group is moved to effectfocusing. Zoom lenses having the above-described focusing system areproposed in Japanese Patent No. 5615143, and Japanese Unexamined PatentPublication Nos. 2012-013817 and 2014-016508 (hereinafter, PatentDocuments 1 to 3, respectively).

SUMMARY

The lenses of Patent Documents 1 to 3, however, have a problem that thesize of the first lens group is extremely large relative to the imagesize. Further, the entire length of the lens of Patent Document 1 islarge, and, in order to reduce the entire length, it is necessary toincrease the power of the first lens group, which will accompany aproblem of insufficient chromatic aberration correction. Also, all thelenses of Patent Documents 2 and 3 have insufficient chromaticaberration correction. In recent years, there is an increasing demandfor portable broadcasting lenses, and high performance lenses that arecompact relative to large image sizes and have successfully correctedchromatic aberration are demanded.

In view of the above-described circumstances, the present disclosure isdirected to providing a compact and high performance zoom lens withsuccessfully corrected chromatic aberration, and an imaging apparatusprovided with the zoom lens.

The zoom lens of the disclosure consists of, in order from the objectside, a first lens group that has a positive refractive power and isfixed during magnification change, at least two movable lens groups thatare moved during magnification change with changing the distances alongthe optical axis direction between adjacent lens groups, and an end lensgroup that has a positive refractive power, is disposed at the mostimage side, and is fixed during magnification change, wherein the firstlens group consists of, in order from the object side, a first-a lensgroup that has a negative refractive power and is fixed during focusing,a first-b lens group that has a positive refractive power and is movedduring focusing with changing the distances along the optical axisdirection between adjacent lens groups, and a first-c lens group thathas a positive refractive power, the first-a lens group includes atleast two negative lenses, wherein the most object-side negative lenshas a meniscus shape with the convex surface toward the object side, anda first-n lens, which is at least one negative lens of the rest of thenegative lenses of the first-a lens group, satisfies the conditionexpressions (1), (2), and (3) below:62<vdn  (1),0.64<θgFn+0.001625×vdn<0.7  (2), and1<fln/fla<2  (3),where vdn is an Abbe number with respect to the d-line of the first-nlens, θgFn is a partial dispersion ratio of the first-n lens, fln is afocal length with respect to the d-line of the first-n lens, and fla isa focal length with respect to the d-line of the first-a lens group.

It is preferred that any one or all of the condition expressions (1-1),(1-2), (2-1), and (3-1) below be satisfied:70<vdn  (1-1),70<vdn<100  (1-2),0.65<θgFn+0.001625×vdn<0.69  (2-1),1.1<fln/fla<1.8  (3-1).

In the zoom lens of the disclosure, it is preferred that the first-alens group include a cemented lens formed by, in order from the objectside, the first-n lens and a first-p lens having a positive refractivepower that are cemented together, and satisfy the condition expressions(4) and (5) below. It is more preferred that the condition expression(4-1) and/or (5-1) below be satisfied.vdp<40  (4),20<vdp<38  (4-1),0.62<θgFp+0.001625×vdp<0.67  (5),0.63<θgFp+0.001625×vdp<0.66  (5-1),where vdp is an Abbe number with respect to the d-line of the first-plens, and θgFp is a partial dispersion ratio of the first-p lens.

It is preferred that the condition expression (6) below be satisfied,and it is more preferred that the condition expression (6-1) below besatisfied:1.2<ft/fl<2  (6),1.3<ft/fl<1.8  (6-1),where ft is a focal length of the entire system at the telephoto end,and fl is a focal length of the first lens group.

It is preferred that the condition expression (7) below be satisfied,and it is more preferred that the condition expression (7-1) below besatisfied:2<flb/fl<4  (7),2.5<flb/fl<3.5  (7-1),where flb is a focal length of the first-b lens group, and fl is a focallength of the first lens group.

It is preferred that the first-a lens group consist of, in order fromthe object side, two negative lenses, and a cemented lens formed by, inorder from the object side, the first-n lens and the first-p lens havinga positive refractive power that are cemented together.

The first-c lens group may be fixed during focusing, or may be movedduring focusing along a different locus of movement from that of thefirst-b lens group.

It is preferred that the movable lens groups comprise at least two lensgroups having a negative refractive power.

It is preferred that the movable lens groups comprise at least threelens groups.

The movable lens groups of the zoom lens may consist of, in order fromthe object side, a second lens group having a positive refractive power,a third lens group having a negative refractive power, and a fourth lensgroup having a negative refractive power, or may consist of, in orderfrom the object side, a second lens group having a positive refractivepower, a third lens group having a negative refractive power, a fourthlens group having a negative refractive power, and a fifth lens grouphaving a positive refractive power.

The imaging apparatus of the disclosure comprises the above-describedzoom lens of the disclosure.

It should be noted that the expression “consisting/consist of” as usedherein means that the zoom lens may include, besides the elementsrecited above: lenses substantially without any power; optical elementsother than lenses, such as a stop, a mask, a cover glass, and filters;and mechanical components, such as a lens flange, a lens barrel, animage sensor, a camera shake correction mechanism, etc.

The sign (positive or negative) with respect to the surface shape andthe refractive power of any lens including an aspheric surface among thelenses described above is about the paraxial region.

The zoom lens of the disclosure consists of, in order from the objectside, a first lens group that has a positive refractive power and isfixed during magnification change, at least two movable lens groups thatare moved during magnification change with changing the distances alongthe optical axis direction between adjacent lens groups, and an end lensgroup that has a positive refractive power, is disposed at the mostimage side, and is fixed during magnification change, wherein the firstlens group consists of, in order from the object side, a first-a lensgroup that has a negative refractive power and is fixed during focusing,a first-b lens group that has a positive refractive power and is movedduring focusing with changing the distances along the optical axisdirection between adjacent lens groups, and a first-c lens group thathas a positive refractive power, the first-a lens group includes atleast two negative lenses, wherein the most object-side negative lenshas a meniscus shape with the convex surface toward the object side, anda first-n lens, which is at least one negative lens of the rest of thenegative lenses of the first-a lens group, satisfies the conditionexpressions (1), (2), and (3) below:62<vdn  (1),0.64<θgFn+0.001625×vdn<0.7  (2),1<fln/fla<2  (3).This configuration allows providing a compact and high performance zoomlens with successfully corrected chromatic aberration.

The imaging apparatus of the disclosure, which is provided with the zoomlens of the disclosure, allows size reduction of the apparatus, andallows obtaining high image-quality images.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating the lens configuration of a zoomlens according to one embodiment of the disclosure (a zoom lens ofExample 1),

FIG. 2 is a sectional view illustrating the lens configuration of a zoomlens of Example 2 of the disclosure,

FIG. 3 is a sectional view illustrating the lens configuration of a zoomlens of Example 3 of the disclosure,

FIG. 4 is a sectional view illustrating the lens configuration of a zoomlens of Example 4 of the disclosure,

FIG. 5 shows aberration diagrams of the zoom lens of Example 1 of thedisclosure,

FIG. 6 shows aberration diagrams of the zoom lens of Example 2 of thedisclosure,

FIG. 7 shows aberration diagrams of the zoom lens of Example 3 of thedisclosure,

FIG. 8 shows aberration diagrams of the zoom lens of Example 4 of thedisclosure,

FIG. 9 is a diagram illustrating the schematic configuration of animaging apparatus according to an embodiment of the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the drawings. FIG. 1 is a sectional viewillustrating the lens configuration of a zoom lens according to oneembodiment of the disclosure. The configuration example shown in FIG. 1is the same as the configuration of a zoom lens of Example 1, which willbe described later. In FIG. 1, the left side is the object side and theright side is the image plane side. An aperture stop St shown in thedrawing does not necessarily represent the size and the shape thereof,but represents the position thereof along the optical axis Z. FIG. 1also shows loci of movement of lens groups during magnification change,an axial bundle of rays wa, and a bundle of rays wb at the maximum angleof view.

The zoom lens of this embodiment consists of, in order from the objectside, a first lens group G1 that has a positive refractive power and isfixed during magnification change, at least two movable lens groups thatare moved during magnification change with changing the distances alongthe optical axis direction between adjacent lens groups, and an end lensgroup that has a positive refractive power, is disposed at the mostimage side, and is fixed during magnification change. In the exampleshown in FIG. 1, the zoom lens consists of the first lens group G1 thathas a positive refractive power and is fixed during magnificationchange, second to fourth lens groups G2 to G4 (movable lens groups) thatare moved during magnification change with changing the distances alongthe optical axis direction between adjacent lens groups, and a fifthlens group G5 (end lens group) that has a positive refractive power, isdisposed at the most image side, and is fixed during magnificationchange. The first lens group G1 consists of ten lenses L1 a to L1 j, thesecond lens group G2 consists of a lens L2 a, the third lens group G3consists of five lenses L3 a to L3 e, the fourth lens group G4 consistsof two lenses L4 a and L4 b, and the fifth lens group G5 consists oftwelve lenses L5 a to L5 l.

When this zoom lens is used with an imaging apparatus, it is preferredto provide a cover glass, a prism, and various filters, such as aninfrared cutoff filter and a low-pass filter, between the optical systemand the image plane Sim depending on the configuration of the camera onwhich the lens is mounted. In the example shown in FIG. 1, opticalmembers PP1 and PP2 in the form of plane-parallel plates, which areassumed to represent the above-mentioned elements, are disposed betweenthe lens system and the image plane Sim.

Providing the most object-side lens group with a positive refractivepower in this manner allows reducing the entire length of the lenssystem, and this is advantageous for size reduction. Further, providingthe most image-side lens group with a positive refractive power allowsminimizing increase of the incidence angle of the principal ray ofoff-axis rays entering the image plane Sim, and this allows suppressingshading. Further, since the most object-side lens group and the mostimage-side lens group are fixed during magnification change, the entirelength of the lens system does not change during magnification change,and this allows providing a zoom lens with small change of center ofgravity during magnification change, and thus with good operability.

The first lens group G1 consists of, in order from the object side, afirst-a lens group G1 a that has a negative refractive power and isfixed during focusing, a first-b lens group G1 b that has a positiverefractive power and is moved during focusing with changing thedistances along the optical axis direction between adjacent lens groups,and a first-c lens group G1 c that has a positive refractive power. Inthis embodiment, the first-a lens group G1 a consists of four lenses L1a to lens L1 d, the first-b lens group G1 b consists of a lens L1 e, andthe first-c lens group G1 c consists of five lenses L1 f to L1 j. Thisconfiguration allows suppressing change of the angle of view duringfocusing.

The first-a lens group G1 a includes at least two negative lenses, wherethe most object-side negative lens has a meniscus shape with the convexsurface toward the object side, and a first-n lens, which is at leastone negative lens of the rest of the negative lenses of the first-a lensgroup, satisfies the condition expressions (1), (2), and (3) below. Inthis embodiment, the lens L1 c corresponds to the first-n lens.

Disposing at least two negative lenses in the first-a lens group G1 a inthis manner allows providing a negative refractive power necessary forachieving a wide angle of view. Providing the most object-side negativelens of the first-a lens group G1 a with a meniscus shape with theconvex surface toward the object side allows suppressing astigmatism anddistortion. Further, providing the first-n lens that satisfies thecondition expressions (1), (2), and (3) below in the first-a lens groupG1 a allows successfully correcting chromatic aberration at the firstlens group G1, in particular, successfully correcting lateral chromaticaberration at the wide angle side and longitudinal chromatic aberrationat the telephoto side.

Satisfying the condition expression (1) allows successfully correctinglateral chromatic aberration at the wide angle side and longitudinalchromatic aberration at the telephoto side during focusing. Further,satisfying the condition expression (2) together with the conditionexpression (1) allows successfully correcting secondary spectrum.Further, satisfying the condition expression (3) allows successfullycorrecting chromatic aberration, in particular, secondary spectrum oflongitudinal chromatic aberration at the telephoto side.62<vdn  (1),0.64<θgFn+0.001625×vdn<0.7  (2), and1<fln/fla<2  (3),where vdn is an Abbe number with respect to the d-line of the first-nlens, θgFn is a partial dispersion ratio of the first-n lens, fln is afocal length with respect to the d-line of the first-n lens, and fla isa focal length with respect to the d-line of the first-a lens group.

It should be noted that higher performance can be obtained when any oneor all of the condition expressions (1-1), (1-2), (2-1), and (3-1) beloware satisfied. Setting the value of vdn such that it does not becomeequal to or greater than the upper limit of the condition expression(1-2) allows preventing the material forming the first-n lens fromhaving excessively low dispersion, and this allows selecting a materialhaving sufficient refractive index for successfully correctingdistortion at the wide angle end.70<vdn  (1-1),70<vdn<100  (1-2),0.65<θgFn+0.001625×vdn<0.69  (2-1),1.1<fln/fla<1.8  (3-1).

In the zoom lens of the disclosure, it is preferred that the first-alens group G1 a include a cemented lens formed by, in order from theobject side, the first-n lens and a first-p lens having a positiverefractive power that are cemented together, and satisfy the conditionexpressions (4) and (5) below. In this embodiment, the lens L1 ccorresponds to the first-n lens, and the lens L1 d corresponds to thefirst-p lens. Disposing the above-described cemented lens in the first-alens group G1 a allows successfully correcting chromatic aberration atthe first-a lens group G1 a, and suppressing change of longitudinalchromatic aberration and lateral chromatic aberration during focusing.Further, satisfying the condition expression (4) allows successfullycorrecting lateral chromatic aberration at the wide angle side andlongitudinal chromatic aberration at the telephoto side during focusing.Satisfying the condition expression (5) together with the conditionexpression (4) allows successfully correcting secondary spectrum. Itshould be noted that higher performance can be obtained when thecondition expression (4-1) and/or (5-1) below is satisfied.vdp<40  (4),20<vdp<38  (4-1),0.62<θgFp+0.001625×vdp<0.67  (5),0.63<θgFp+0.001625×vdp<0.66  (5-1),where vdp is an Abbe number with respect to the d-line of the first-plens, and θgFp is a partial dispersion ratio of the first-p lens.

Further, it is preferred that the condition expression (6) below besatisfied. Setting the value of ft/fl such that it does not become equalto or smaller than the lower limit of the condition expression (6)allows preventing the power of the first lens group G1 from becomingexcessively weak, and this prevents increase of the entire length,thereby contributing to size reduction. Setting the value of ft/fl suchthat it does not become equal to or greater than the upper limit of thecondition expression (6) allows preventing the power of the first lensgroup G1 from becoming excessively strong, and this allows successfullycorrecting chromatic aberration. It should be noted that higherperformance can be obtained when the condition expression (6-1) below issatisfied.1.2<ft/fl<2  (6),1.3<ft/fl<1.8  (6-1),where ft is a focal length of the entire system at the telephoto end,and fl is a focal length of the first lens group.

It is preferred that the condition expression (7) below be satisfied.Satisfying the condition expression (7) allows suppressing change ofaberrations during focusing. In particular, setting the value of flb/flsuch that it does not become equal to or smaller than the lower limit ofthe condition expression (7) allows preventing the power from becomingexcessively strong, and this allows suppressing change of aberrationsduring focusing. Setting the value of flb/fl such that it does notbecome equal to or greater than the upper limit of condition expression(7) allows preventing the amount of movement of the first-b lens groupG1 b during focusing from becoming excessively large, and thiscontributes to size reduction of the first lens group G1. It should benoted that higher performance can be obtained when the conditionexpression (7-1) below is satisfied.2<flb/fl<4  (7),2.5<flb/fl<3.5  (7-1),where flb is a focal length of the first-b lens group, and fl is a focallength of the first lens group.

Further, it is preferred that the first-a lens group G1 a consist of, inorder from the object side, two negative lenses, and a cemented lensformed by, in order from the object side, the first-n lens and thefirst-p lens having a positive refractive power that are cementedtogether. This configuration allows suppressing field curvature anddistortion at the wide angle side, and successfully correcting sphericalaberration at the telephoto side.

The first-c lens group G1 c may be fixed during focusing. In this case,the first-b lens group G1 b is the only movable group during focusing,and this allows weight reduction of the movable group that is movedduring focusing.

The first-c lens group G1 c may be moved during focusing along adifferent locus of movement from that of the first-b lens group G1 b.This configuration facilitates suppressing change of aberrations duringfocusing, in particular, facilitates suppressing field curvature anddistortion at the wide angle side, and spherical aberration at thetelephoto side.

It is preferred that the movable lens groups include at least two lensgroups having a negative refractive power. In general, when there aretwo movable lens groups having a negative refractive power, the amountof movement of the movable lens groups can be made smaller than thatwhen there is one movable lens group having a negative refractive power.This configuration therefore leads to reduction of the entire length ofthe lens system.

It is preferred that the movable lens groups include at least threemovable lens groups. This configuration facilitates correction ofaberrations during magnification change, in particular, facilitatessuppressing change of spherical aberration, field curvature, anddistortion.

The movable lens groups of the zoom lens may consist of, in order fromthe object side, the second lens group G2 having a positive refractivepower, the third lens group G3 having a negative refractive power, andthe fourth lens group G4 having a negative refractive power. Thisconfiguration facilitates correction of aberrations during magnificationchange, in particular, facilitates suppressing change of sphericalaberration, field curvature, and distortion. It should be noted that thezoom lens of this embodiment shows this aspect.

Alternatively, the movable lens groups of the zoom lens may consist of,in order from the object side, the second lens group having a positiverefractive power, the third lens group having a negative refractivepower, the fourth lens group having a negative refractive power, and thefifth lens group having a positive refractive power. This configurationallows more appropriate aberration correction than the above-describedconfiguration where the movable lens groups consists of three lensgroups.

In the example shown in FIG. 1, the optical members PP1 and PP2 aredisposed between the lens system and the image plane Sim. However, inplace of disposing the various filters, such as a low-pass filter and afilter that cuts off a specific wavelength range, between the lenssystem and the image plane Sim, the various filters may be disposedbetween the lenses, or coatings having the same functions as the variousfilters may be applied to the lens surfaces of some of the lenses.

Next, numerical examples of the zoom lens of the disclosure aredescribed.

First, a zoom lens of Example 1 is described. FIG. 1 is a sectional viewillustrating the lens configuration of the zoom lens of Example 1. Itshould be noted that, in FIG. 1, and FIGS. 2 to 4 corresponding toExamples 2 to 4, which will be described later, the left side is theobject side and the right side is the image plane side. The aperturestop St shown in the drawings does not necessarily represent the sizeand the shape thereof, but represents the position thereof along theoptical axis Z. FIG. 1 also shows loci of movement of the lens groupsduring magnification change, an axial bundle of rays wa, and a bundle ofrays wb at the maximum angle of view.

The zoom lens of Example 1 consists of, in order from the object side, afirst lens group G1 that has a positive refractive power and is fixedduring magnification change, second to fourth lens groups G2 to G4(movable lens groups) that are moved during magnification change withchanging the distances along the optical axis direction between adjacentlens groups, and a fifth lens group G5 (end lens group) that has apositive refractive power, is disposed at the most image side, and isfixed during magnification change.

Table 1 shows basic lens data of the zoom lens of Example 1, Table 2shows data about specifications of the zoom lens, Table 3 shows dataabout variable surface distances of the zoom lens, and Table 4 showsdata about aspheric coefficients of the zoom lens. In the followingdescription, meanings of symbols used in the tables are explained withrespect to Example 1 as an example. The same explanations basicallyapply to those with respect to Examples 2 to 4.

In the lens data shown in Table 1, each value in the column of “SurfaceNo.” represents a surface number, where the object-side surface of themost object-side element is the 1st surface and the number issequentially increased toward the image plane side, each value in thecolumn of “Radius of Curvature” represents the radius of curvature ofthe corresponding surface, and each value in the column of “SurfaceDistance” represents the distance along the optical axis Z between thecorresponding surface and the next surface. Each value in the column of“nd” represents the refractive index with respect to the d-line (thewavelength of 587.6 nm) of the corresponding optical element, each valuein the column of “vd” represents the Abbe number with respect to thed-line (the wavelength of 587.6 nm) of the corresponding opticalelement, and each value in the column of “θgF” represents the partialdispersion ratio of the corresponding optical element.

It should be noted that the partial dispersion ratio θgF is expressed bythe formula below:θgF=(Ng−NF)/(NF−NC),where Ng is a refractive index with respect to the g-line, NF is arefractive index with respect to F-line, and NC is a refractive indexwith respect to the C-line.

The sign with respect to the radius of curvature is provided such that apositive radius of curvature indicates a surface shape that is convextoward the object side, and a negative radius of curvature indicates asurface shape that is convex toward the image plane side. The basic lensdata also includes data about the aperture stop St and the opticalmembers PP1 and PP2, and the surface number and the text “(stop)” areshown at the position in the column of the surface number correspondingto the aperture stop St. In the lens data shown in Table 1, each surfacedistance that is variable during magnification change is represented bythe symbol “DD[surface number]”. The numerical value corresponding toeach DD[surface number] is shown in Table 3.

The data about specifications shown in Table 2 show values of zoommagnification, focal length f, F-number FNo, and full angle of view 2ω.

With respect to the basic lens data, the data about specifications, andthe data about variable surface distances, the unit of angle is degrees,and the unit of length is millimeters; however, any other suitable unitsmay be used since optical systems are usable when they areproportionally enlarged or reduced.

In the lens data shown in Table 1, the symbol “*” is added to thesurface number of each aspheric surface, and the numerical value of theparaxial radius of curvature is shown as the radius of curvature of eachaspheric surface. In the data about aspheric coefficients shown in Table4, the surface number of each aspheric surface and aspheric coefficientsabout each aspheric surface are shown. The aspheric coefficients arevalues of the coefficients KA and Am (where m=3, . . . , 20) in theformula of aspheric surface shown below:Zd=C·h ²/{1+(1−KA·C ² ·h ²)^(1/2) }+ΣAm·h ^(m),where Zd is a depth of the aspheric surface (a length of a perpendicularline from a point with a height h on the aspheric surface to a planetangent to the apex of the aspheric surface and perpendicular to theoptical axis), h is the height (a distance from the optical axis), C isa reciprocal of the paraxial radius of curvature, and KA and Am areaspheric coefficients (where m=3, . . . , 20).

TABLE 1 Example 1 - Lens Data Radius of Surface No. Curvature SurfaceDistance nd νd θgF  1 214.0485 3.6001 1.88300 40.76 0.56679  2 75.163022.9827  3 −597.4831 3.3000 1.73400 51.47 0.54874  4 443.5473 12.9081  5−187.4186 5.8583 1.53775 74.70 0.53936  6 122.1466 14.7216 1.91650 31.600.59117  7 −1192.6629 2.6958  *8 337.3004 13.7943 1.43875 94.94 0.53433 9 −172.5134 13.4076  10 192.0693 17.0129 1.49700 81.54 0.53748  11−139.9406 0.6538  12 −133.1303 3.3500 1.85150 40.78 0.56958  13 115.273315.2541 1.49700 81.54 0.53748  14 −398.0807 6.0395  15 459.0857 12.90201.53775 74.70 0.53936  16 −156.6756 0.2000  17 137.1994 15.6658 1.4970081.54 0.53748  18 −276.3776 DD[18]  19 362.4361 2.9957 1.49700 81.540.53748  20 −555.5230 DD[20] *21 212.6957 2.4011 1.53775 74.70 0.53936 22 27.2627 10.4426  23 −42.9639 1.2004 2.00100 29.13 0.59952  24191.3068 2.4309  25 −105.3359 6.7325 1.69895 30.13 0.60298  26 −28.81192.4783 1.69560 59.05 0.54348  27 −82.6623 0.3007  28 161.3383 5.24911.83481 42.72 0.56486  29 −80.5118 DD[29]  30 −52.0619 1.3100 1.4970081.54 0.53748  31 1116.7924 1.9941 1.84666 23.83 0.61603  32 −307.6714DD[32]  33 (stop) ∞ 1.8275  34 118.3571 3.8140 1.91082 35.25 0.58224  35−350.3523 2.5727  36 −105.5123 3.0000 1.76182 26.52 0.61361  37−208.3315 11.3437  38 59.9113 5.2848 1.65844 50.88 0.55612  39 ∞ 0.3009 40 42.0799 10.3271 1.43875 94.94 0.53433  41 −78.3277 1.5500 1.9537532.32 0.59015  42 56.6019 4.9263  43 −226.8790 6.1786 1.80518 25.430.61027  44 −36.3203 1.4100 1.80400 46.58 0.55730  45 −106.9554 0.4084 46 64.4975 7.8638 1.48749 70.24 0.53007  47 −64.4975 0.2001  48 54.52072.0998 1.91082 35.25 0.58224  49 20.5114 13.6195 1.49700 81.54 0.53748 50 −42.0493 1.6000 1.90043 37.37 0.57720  51 57.4339 0.6085  52 48.26443.3704 1.84666 23.83 0.61603  53 240.7851 3.0000  54 ∞ 1.4000 1.5163364.14 0.53531  55 ∞ 1.0000  56 ∞ 3.6900 1.51633 64.14 0.53531  57 ∞54.0311

TABLE 2 Example 1 - Specifications (d-line) Wide Angle End MiddleTelephoto End Zoom Magnification 1.0 2.4 7.4 f′ 19.91 46.80 146.33 FNo.2.86 2.86 2.86 2ω[°] 73.6 33.2 11.0

TABLE 3 Example 1 - Distances with respect to Zoom Wide Angle End MiddleTelephoto End DD[18] 1.4993 49.5135 85.3829 DD[20] 1.4865 6.8361 8.7457DD[29] 62.9756 9.2695 21.2659 DD[32] 52.4033 52.7456 2.9702

TABLE 4 Example 1 - Aspheric Coefficients Surface No. 8 KA 1.0000000E+00A3 1.5064530E−07 A4 −1.5641141E−07  A5 1.6501598E−09 A6 −3.9701428E−11 A7 6.9263338E−13 A8 1.0556630E−17 A9 −7.0509369E−17  A10 5.3287613E−19Surface No. 21 KA  1.0000000E+00 A4  1.5045420E−06 A6 −4.1679388E−10 A8−8.9800509E−12 A10  7.0993908E−14 A12 −3.2299521E−16 A14  8.7823289E−19A16 −1.4036759E−21 A18  1.2097861E−24 A20 −4.3023907E−28

FIG. 5 shows aberration diagrams of the zoom lens of Example 1. Theaberration diagrams shown at the top of FIG. 5 are those of sphericalaberration, astigmatism, distortion, and lateral chromatic aberration,in this order from the left side, at the wide-angle end. The aberrationdiagrams shown at the middle of FIG. 5 are those of sphericalaberration, astigmatism, distortion, and lateral chromatic aberration,in this order from the left side, at the middle position. The aberrationdiagrams shown at the bottom of FIG. 5 are those of sphericalaberration, distortion, and lateral chromatic aberration, in this orderfrom the left side, at the telephoto end. These aberration diagrams showaberrations when the object distance is infinity. The aberrationdiagrams of spherical aberration, astigmatism, and distortion show thosewith respect to the d-line (the wavelength of 587.6 nm), which is usedas a reference wavelength. The aberration diagrams of sphericalaberration show those with respect to the d-line (the wavelength of587.6 nm), the C-line (the wavelength of 656.3 nm), the F-line (thewavelength of 486.1 nm), and the g-line (the wavelength of 435.8 nm) inthe solid line, the long dashed line, the short dashed line, and thegray solid line, respectively. The aberration diagrams of astigmatismshow those in the sagittal direction and the tangential direction in thesolid line, and the short dashed line, respectively. The aberrationdiagrams of lateral chromatic aberration show those with respect to theC-line (the wavelength of 656.3 nm), the F-line (the wavelength of 486.1nm), and the g-line (the wavelength of 435.8 nm) in the long dashedline, the short dashed line, and the gray solid line, respectively. Thesymbol “FNo.” in the aberration diagrams of spherical aberration means“F-number”, and the symbol “ω” in the other aberration diagrams means“half angle of view”.

Next, a zoom lens of Example 2 is described. FIG. 2 is a sectional viewillustrating the lens configuration of the zoom lens of Example 2. Thezoom lens of Example 2 consists of in order from the object side, afirst lens group G1 that has a positive refractive power and is fixedduring magnification change, second to fifth lens groups G2 to G5(movable lens groups) that are moved during magnification change withchanging the distances along the optical axis direction between adjacentlens groups, and a sixth lens group G6 (end lens group) that has apositive refractive power, is disposed at the most image side, and isfixed during magnification change. The first lens group G1 consists often lenses L1 a to L1 j, the second lens group G2 consists of a lens L2a, the third lens group G3 consists of five lenses L1 a to L3 e, thefourth lens group G4 consists of two lenses L4 a and L4 b, the fifthlens group G5 consists of two lenses L5 a and L5 b, and the sixth lensgroup G6 consists of ten lenses L6 a to L6 j. Table 5 shows basic lensdata of the zoom lens of Example 2, Table 6 shows data aboutspecifications of the zoom lens, Table 7 shows data about variablesurface distances of the zoom lens, Table 8 shows data about asphericcoefficients of the zoom lens, and FIG. 6 shows aberration diagrams ofthe zoom lens.

TABLE 5 Example 2 - Lens Data Radius of Surface No. Curvature SurfaceDistance nd νd θgF  1 204.5076 3.6001 1.88300 40.76 0.56679  2 75.157726.8271  3 −680.1918 3.3001 1.73400 51.47 0.54874  4 394.2434 10.1996  5−194.8976 6.0275 1.53775 74.70 0.53936  6 119.9249 14.7493 1.91650 31.600.59117  7 −1395.5679 1.4975  *8 334.5227 13.5447 1.43875 94.94 0.53433 9 −178.4244 13.8156  10 190.5673 16.5365 1.49700 81.54 0.53748  11−148.2904 0.8631  12 −137.7176 3.3505 1.85150 40.78 0.56958  13 113.914015.3310 1.49700 81.54 0.53748  14 −407.0823 5.3500  15 573.8699 13.37191.53775 74.70 0.53936  16 −155.6554 0.2451  17 138.0910 16.3580 1.4970081.54 0.53748  18 −248.2025 DD[18]  19 331.9810 3.0337 1.49700 81.540.53748  20 −566.9344 DD[20] *21 236.4764 2.3725 1.53775 74.70 0.53936 22 27.4357 10.1724  23 −43.6440 1.2000 2.00100 29.13 0.59952  24196.3935 2.3659  25 −105.3852 6.3996 1.69895 30.13 0.60298  26 −29.47774.4704 1.69560 59.05 0.54348  27 −84.3847 0.3005  28 170.5472 5.10641.83481 42.72 0.56486  29 −82.5546 DD[29]  30 −52.8642 1.3101 1.4970081.54 0.53748  31 1177.9980 1.9548 1.84666 23.83 0.61603  32 −319.2827DD[32]  33 (stop) ∞ 1.1696  34 117.8758 3.7936 1.91082 35.25 0.58224  35−345.2428 2.2403  36 −103.1702 3.0000 1.76182 26.52 0.61361  37−203.4153 DD[37]  38 60.3391 5.2627 1.65844 50.88 0.55612  39 ∞ 0.8372 40 41.6543 10.3088 1.43875 94.94 0.53433  41 −77.6159 1.5892 1.9537532.32 0.59015  42 55.9588 4.8039  43 −243.7036 6.2713 1.80518 25.430.61027  44 −35.9951 1.4100 1.80400 46.58 0.55730  45 −106.5175 0.6156 46 63.7897 7.9106 1.48749 70.24 0.53007  47 −63.7897 0.2007  48 54.47701.6010 1.91082 35.25 0.58224  49 20.5144 14.2437 1.49700 81.54 0.53748 50 −41.6177 1.6006 1.90043 37.37 0.57720  51 57.8925 0.3412  52 48.50573.3350 1.84666 23.83 0.61603  53 242.4352 3.0000  54 ∞ 1.4000 1.5163364.14 0.53531  55 ∞ 1.0000  56 ∞ 3.6900 1.51633 64.14 0.53531  57 ∞52.9818

TABLE 6 Example 2 - Specifications (d-line) Wide Angle End MiddleTelephoto End Zoom Magnification 1.0 2.4 7.4 f′ 19.88 46.74 146.14 FNo.2.86 2.86 2.86 2ω[°] 73.8 33.2 11.0

TABLE 7 Example 2 - Distances with respect to Zoom Wide Angle End MiddleTelephoto End DD[18] 1.4998 51.1925 88.2200 DD[20] 1.4938 6.8434 8.7530DD[29] 64.3039 9.6273 20.8055 DD[32] 51.9906 52.1819 2.9978 DD[37]10.1220 9.5650 8.6338

TABLE 8 Example 2 - Aspheric Coefficients Surface No. 8 KA 1.0000000E+00A3 1.5064530E−07 A4 −1.5641141E−07  A5 1.6501598E−09 A6 −3.9701428E−11 A7 6.9263338E−13 A8 1.0556630E−17 A9 −7.0509369E−17  A10 5.3287613E−19Surface No. 21 KA  1.0000000E+00 A4  1.5045420E−06 A6 −4.1679388E−10 A8−8.9800509E−12 A10  7.0993908E−14 A12 −3.2299521E−16 A14  8.7823289E−19A16 −1.4036759E−21 A18  1.2097861E−24 A20 −4.3023907E−28

Next, a zoom lens of Example 3 is described. FIG. 3 is a sectional viewillustrating the lens configuration of the zoom lens of Example 3. Thezoom lens of Example 3 has the same lens group configuration as that ofthe zoom lens of Example 1. Table 9 shows basic lens data of the zoomlens of Example 3, Table 10 shows data about specifications of the zoomlens, Table 11 shows data about variable surface distances of the zoomlens, Table 12 shows data about aspheric coefficients of the zoom lens,and FIG. 7 shows aberration diagrams of the zoom lens.

TABLE 9 Example 3 - Lens Data Radius of Surface No. Curvature SurfaceDistance nd νd θgF  1 203.3033 3.6000 1.75500 52.32 0.54765  2 70.939127.1004  3 −338.7454 3.3001 1.77250 49.60 0.55212  4 378.5456 10.5278  5−265.5030 3.5300 1.43875 94.66 0.53402  6 122.8648 13.6010 1.91082 35.250.58224  7 −19851.3347 3.6816  *8 281.3047 12.9599 1.43875 94.94 0.53433 9 −214.8359 14.8527  10 238.5428 15.5435 1.49700 81.54 0.53748  11−142.9598 0.5234  12 −137.9389 3.3500 1.83481 42.72 0.56486  13 106.136017.0654 1.49700 81.54 0.53748  14 −316.9974 0.4827  15 543.8380 11.01821.53775 74.70 0.53936  16 −177.9557 2.8866  17 133.2953 17.4933 1.4970081.54 0.53748  18 −208.4111 DD[18]  19 349.0362 3.0377 1.49700 81.540.53748  20 −585.2849 DD[20] *21 231.8394 2.3423 1.53775 74.70 0.53936 22 27.2866 10.6024  23 −43.2897 1.2000 2.00100 29.13 0.59952  24203.7558 2.8071  25 −102.0549 6.6695 1.69895 30.13 0.60298  26 −29.21081.7290 1.69560 59.05 0.54348  27 −80.5930 0.3005  28 161.3029 5.23951.83481 42.72 0.56486  29 −80.8454 DD[29]  30 −52.3914 1.3100 1.4970081.54 0.53748  31 3010.3139 1.9234 1.84666 23.83 0.61603  32 −274.0259DD[32]  33 (stop) ∞ 2.0283  34 119.4012 3.5996 1.91082 35.25 0.58224  35−414.6305 1.6311  36 −106.0887 3.0000 1.76182 26.52 0.61361  37−192.8743 11.6874  38 62.8957 5.0727 1.65844 50.88 0.55612  39 ∞ 0.3004 40 42.0886 10.3576 1.43875 94.94 0.53433  41 −78.0793 1.4003 1.9537532.32 0.59015  42 55.8551 6.2257  43 −253.7994 6.5210 1.80518 25.430.61027  44 −36.2933 1.4100 1.80400 46.58 0.55730  45 −105.8885 0.2000 46 64.2148 8.2858 1.48749 70.24 0.53007  47 −64.2148 0.2000  48 55.23512.2417 1.91082 35.25 0.58224  49 20.9380 14.8846 1.49700 81.54 0.53748 50 −43.1405 1.6000 1.90043 37.37 0.57720  51 58.6237 0.2008  52 46.26595.8212 1.84666 23.83 0.61603  53 184.1153 3.0000  54 ∞ 1.4000 1.5163364.14 0.53531  55 ∞ 1.0000  56 ∞ 3.6900 1.51633 64.14 0.53531  57 ∞51.2846

TABLE 10 Example 3 - Specifications (d-line) Wide Angle End MiddleTelephoto End Zoom Magnification 1.0 2.4 7.4 f′ 19.90 46.79 146.29 FNo.2.86 2.86 2.86 2ω[°] 73.8 33.2 11.0

TABLE 11 Example 3 - Distances with respect to Zoom Wide Angle EndMiddle Telephoto End DD[18] 1.4998 50.0802 86.4555 DD[20] 1.4969 6.84658.7561 DD[29] 64.0006 9.2167 21.7032 DD[32] 52.8723 53.7262 2.9548

TABLE 12 Example 3 - Aspheric Coefficients Surface No. 8 KA1.0000000E+00 A3 1.5064530E−07 A4 −1.5641141E−07  A5 1.6501598E−09 A6−3.9701428E−11  A7 6.9263338E−13 A8 1.0556630E−17 A9 −7.0509369E−17  A105.3287613E−19 Surface No. 21 KA  1.0000000E+00 A4  1.5045420E−06 A6−4.1679388E−10 A8 −8.9800509E−12 A10  7.0993908E−14 A12 −3.2299521E−16A14  8.7823289E−19 A16 −1.4036759E−21 A18  1.2097861E−24 A20−4.3023907E−28

Next, a zoom lens of Example 4 is described. FIG. 4 is a sectional viewillustrating the lens configuration of the zoom lens of Example 4. Thezoom lens of Example 4 has the same lens group configuration as that ofthe zoom lens of Example 1. Table 13 shows basic lens data of the zoomlens of Example 4, Table 14 shows data about specifications of the zoomlens, Table 15 shows data about variable surface distances of the zoomlens, Table 16 shows data about aspheric coefficients of the zoom lens,and FIG. 8 shows aberration diagrams of the zoom lens.

TABLE 13 Example 4 - Lens Data Radius of Surface No. Curvature SurfaceDistance nd νd θgF  1 206.2478 3.6000 1.83481 42.72 0.56486  2 73.675528.3630  3 −414.1587 3.3001 1.80400 46.58 0.55730  4 378.1742 10.0697  5−203.7117 3.5307 1.49700 81.54 0.53748  6 126.7830 14.8567 1.91650 31.600.59117  7 −800.5290 1.4943  *8 333.3336 13.3218 1.43875 94.94 0.53433 9 −183.4719 14.0204  10 199.5391 17.3922 1.49700 81.54 0.53748  11−131.2369 0.3242  12 −128.6939 3.3505 1.85150 40.78 0.56958  13 115.091015.6314 1.49700 81.54 0.53748  14 −355.9889 6.5632  15 459.3712 12.98181.53775 74.70 0.53936  16 −156.5869 0.2014  17 137.0094 15.6708 1.4970081.54 0.53748  18 −277.4188 DD[18]  19 360.3858 3.0389 1.49700 81.540.53748  20 −557.9596 DD[20] *21 216.3200 2.4009 1.53775 74.70 0.53936 22 27.2953 10.4367  23 −42.9945 1.2000 2.00100 29.13 0.59952  24192.1280 2.4232  25 −105.2604 6.7166 1.69895 30.13 0.60298  26 −28.83102.6322 1.69560 59.05 0.54348  27 −82.9675 0.3000  28 162.6223 5.23441.83481 42.72 0.56486  29 −80.5636 DD[29]  30 −51.8139 1.3100 1.4970081.54 0.53748  31 1155.8690 1.9895 1.84666 23.83 0.61603  32 −303.9788DD[32]  33 (stop) ∞ 2.5109  34 118.6003 3.8001 1.91082 35.25 0.58224  35−340.2735 2.5000  36 −105.2797 3.0000 1.76182 26.52 0.61361  37−211.7385 10.7447  38 59.6286 5.2859 1.65844 50.88 0.55612  39 ∞ 0.7143 40 42.1381 10.1467 1.43875 94.94 0.53433  41 −79.4704 1.4000 1.9537532.32 0.59015  42 57.3111 4.8082  43 −211.6643 5.9778 1.80518 25.430.61027  44 −36.7566 1.4100 1.80400 46.58 0.55730  45 −107.9111 0.2974 46 65.4459 7.6951 1.48749 70.24 0.53007  47 −65.4459 0.9133  48 52.80611.6002 1.91082 35.25 0.58224  49 20.4963 12.8564 1.49700 81.54 0.53748 50 −42.9103 1.6003 1.90043 37.37 0.57720  51 57.8695 1.1479  52 49.79503.2238 1.84666 23.83 0.61603  53 250.6338 3.0000  54 ∞ 1.4000 1.5163364.14 0.53531  55 ∞ 1.0000  56 ∞ 3.6900 1.51633 64.14 0.53531  57 ∞54.3476

TABLE 14 Example 4 - Specifications (d-line) Wide Angle End MiddleTelephoto End Zoom Magnification 1.0 2.4 7.4 f′ 19.85 46.66 145.88 FNo.2.85 2.85 2.85 2ω[°] 73.8 33.4 11.0

TABLE 15 Example 4 - Distances with respect to Zoom Wide Angle EndMiddle Telephoto End DD[18] 1.4999 48.9126 84.7378 DD[20] 1.6030 7.39509.3351 DD[29] 62.7958 9.3474 21.1948 DD[32] 52.3243 52.5680 2.9554

TABLE 16 Example 4 - Aspheric Coefficients Surface No. 8 KA1.0000000E+00 A3 1.5064530E−07 A4 −1.5641141E−07  A5 1.6501598E−09 A6−3.9701428E−11  A7 6.9263338E−13 A8 1.0556630E−17 A9 −7.0509369E−17  A105.3287613E−19 Surface No. 21 KA  1.0000000E+00 A4  1.5045420E−06 A6−4.1679388E−10 A8 −8.9800509E−12 A10  7.0993908E−14 A12 −3.2299521E−16A14  8.7823289E−19 A16 −1.4036759E−21 A18  1.2097861E−24 A20−4.3023907E−28

Table 17 shows values corresponding to the condition expressions (1) to(7) of the zoom lenses of Examples 1 to 4. In all the examples, thed-line is used as a reference wavelength, and the values shown in theTable 17 below are with respect to the reference wavelength.

TABLE 17 Condition Example Example Example Example No. Expression 1 2 34 (1) 62 < νdn 74.70 74.70 94.66 81.54 (2) 0.64 < θgFn + 0.66075 0.660750.68784 0.66999 0.001625 × νdn < 0.7 (3) 1 < fln/fla < 2 1.273 1.2621.696 1.433 (4) νdp < 40 31.60 31.60 35.25 31.60 (5) 0.62 < θgFp +0.64253 0.64253 0.63953 0.64253 0.001625 × νdp < 0.67 (6) 1.2 < ft/fl <2 1.592 1.543 1.537 1.585 (7) 2 < flb/fl < 4 2.854 2.823 2.940 2.954

As can be seen from the above-described data, all the zoom lenses ofExamples 1 to 4 satisfy the condition expressions (1) to (7), and arecompact and high performance zoom lenses with successfully correctedchromatic aberration, while ensuring a zoom ratio of around 7×.

Next, an imaging apparatus according to an embodiment of the disclosureis described. FIG. 9 is a diagram illustrating the schematicconfiguration of an imaging apparatus employing the zoom lens of theembodiment of the disclosure, which is one example of the imagingapparatus of the embodiment of the disclosure. It should be noted thatthe lens groups are schematically shown in FIG. 9. Examples of theimaging apparatus may include a video camera, an electronic stillcamera, etc., which include a solid-state image sensor, such as a CCD(Charge Coupled Device) or CMOS (Complementary Metal OxideSemiconductor), serving as a recording medium.

The imaging apparatus 10 shown in FIG. 9 includes: a zoom lens 1; afilter 6 having a function of a low-pass filter, etc., disposed on theimage plane side of the zoom lens 1; an image sensor 7 disposed on theimage plane side of the filter 6; and a signal processing circuit 8. Theimage sensor 7 converts an optical image formed by the zoom lens 1 intoan electric signal. As the image sensor 7, a CCD or a CMOS, for example,may be used. The image sensor 7 is disposed such that the imagingsurface thereof is positioned in the same position as the image plane ofthe zoom lens 1.

An image taken through the zoom lens 1 is formed on the imaging surfaceof the image sensor 7. Then, a signal about the image outputted from theimage sensor 7 is processed by the signal processing circuit 8, and theimage is displayed on a display unit 9.

The imaging apparatus 10 of this embodiment is provided with the zoomlens 1 of the disclosure, and therefore allows size reduction of theapparatus, and obtaining high image-quality images.

The present disclosure has been described with reference to theembodiments and the examples. However, the disclosure is not limited tothe above-described embodiments and examples, and various modificationsmay be made to the disclosure. For example, the values of the radius ofcurvature, the surface distance, the refractive index, the Abbe number,etc., of each lens element are not limited to the values shown in theabove-described numerical examples and may be different values.

What is claimed is:
 1. A zoom lens consists of, in order from the objectside, a first lens group that has a positive refractive power and isfixed during magnification change, at least two movable lens groups thatare moved during magnification change with changing the distances alongthe optical axis direction between adjacent lens groups, and an end lensgroup that has a positive refractive power, is disposed at the mostimage side, and is fixed during magnification change, wherein the firstlens group consists of, in order from the object side, a first-a lensgroup that has a negative refractive power and is fixed during focusing,a first-b lens group that has a positive refractive power and is movedduring focusing with changing the distances along the optical axisdirection between adjacent lens groups, and a first-c lens group thathas a positive refractive power, the first-a lens group includes atleast two negative lenses, wherein the most object-side negative lenshas a meniscus shape with the convex surface toward the object side, anda first-n lens, which is at least one negative lens of the rest of thenegative lenses of the first-a lens group, satisfies the conditionexpressions (1), (2), and (3) below:62<vdn  (1),0.64<θgFn+0.001625×vdn<0.7  (2), and1<fln/fla<2  (3), where vdn is an Abbe number with respect to the d-lineof the first-n lens, θgFn is a partial dispersion ratio of the first-nlens, fln is a focal length with respect to the d-line of the first-nlens, and fla is a focal length with respect to the d-line of thefirst-a lens group.
 2. The zoom lens as claimed in claim 1, wherein thefirst-a lens group includes a cemented lens formed by, in order from theobject side, the first-n lens and a first-p lens having a positiverefractive power that are cemented together, and satisfies the conditionexpressions (4) and (5) below:vdp<40  (4), and0.62<θgFp+0.001625×vdp<0.67  (5), where vdp is an Abbe number withrespect to the d-line of the first-p lens, and θgFp is a partialdispersion ratio of the first-p lens.
 3. The zoom lens as claimed inclaim 2, wherein the condition expression (4-1) below is satisfied:20<vdp<38  (4-1).
 4. The zoom lens as claimed in claim 2, wherein thecondition expression (5-1) below is satisfied:0.63<θgFp+0.001625×vdp<0.66  (5-1).
 5. The zoom lens as claimed in claim1, wherein the condition expression (6) below is satisfied:1.2<ft/fl<2  (6), where ft is a focal length of the entire system at thetelephoto end, and fl is a focal length of the first lens group.
 6. Thezoom lens as claimed in claim 5, wherein the condition expression (6-1)below is satisfied:1.3<ft/fl<1.8  (6-1).
 7. The zoom lens as claimed in claim 1, whereinthe condition expression (7) below is satisfied:2<flb/fl<4  (7), where flb is a focal length of the first-b lens group,and fl is a focal length of the first lens group.
 8. The zoom lens asclaimed in claim 7, wherein the condition expression (7-1) below issatisfied:2.5<flb/fl<3.5  (7-1).
 9. The zoom lens as claimed in claim 1, whereinthe first-a lens group consists of, in order from the object side, twonegative lenses, and a cemented lens formed by, in order from the objectside, the first-n lens and a first-p lens having a positive refractivepower that are cemented together.
 10. The zoom lens as claimed in claim1, wherein the first-c lens group is fixed during focusing.
 11. The zoomlens as claimed in claim 1, wherein the first-c lens group is movedduring focusing along a different locus of movement from that of thefirst-b lens group.
 12. The zoom lens as claimed in claim 1, wherein themovable lens groups comprises at least two lens groups having a negativerefractive power.
 13. The zoom lens as claimed in claim 1, wherein themovable lens groups comprises at least three lens groups.
 14. The zoomlens as claimed in claim 1, wherein the at least two movable lens groupsconsists of, in order from the object side, a second lens group having apositive refractive power, a third lens group having a negativerefractive power, and a fourth lens group having a negative refractivepower.
 15. The zoom lens as claimed in claim 1, wherein the at least twomovable lens groups consists of, in order from the object side, a secondlens group having a positive refractive power, a third lens group havinga negative refractive power, a fourth lens group having a negativerefractive power, and a fifth lens group having a positive refractivepower.
 16. The zoom lens as claimed in claim 1, wherein the conditionexpression (1-1) below is satisfied:70<vdn  (1-1).
 17. The zoom lens as claimed in claim 16, wherein thecondition expression (1-2) below is satisfied:70<vdn<100  (1-2).
 18. The zoom lens as claimed in claim 1 wherein thecondition expression (2-1) below is satisfied:0.65<θgFn+0.001625×vdn<0.69  (2-1).
 19. The zoom lens as claimed inclaim 1, wherein the condition expression (3-1) below is satisfied:1.1<fln/fla<1.8  (3-1).
 20. An imaging apparatus comprising the zoomlens as claimed in claim 1.